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排序方式: 共有7965条查询结果,搜索用时 31 毫秒
991.
《Journal of the European Ceramic Society》2022,42(3):1014-1022
In this work we have investigated the effect of the solvent during the processing of SrFe12O19 platelet-based permanent magnets by cold sintering process (CSP) plus a post-thermal treatment. Several organic solvents: glacial acetic acid, oleic acid and oleylamine have been analyzed, optimizing the CSP temperatures at 190?270 °C, under pressures of 375?670 MPa and 6?50 wt% of solvent. Modifications in the morphological and structural properties are identified depending on the solvent, which impacts on the magnetic response. Independently of the solvent, the mechanical integrity of ferrite magnets obtained by CSP is improved by a post-annealing at 1100 °C for 2 h, resulting in relative densities around 92 % with an average grain size of 1 μm and a fraction of SrFe12O19 phase >91 %. HC ≥ 2.1 kOe and MS of 73 emu/g are obtained in the final sintered ceramic magnets, exhibiting the highest HC value of 2.8 kOe for the magnet sintered using glacial acetic acid. 相似文献
992.
《Journal of the European Ceramic Society》2021,41(14):7085-7097
Optimization of materials exhibiting high-temperature superconductivity for producing controllable nano-devices is crucial for industrial applications. Herein we report a comprehensive study of the diffusion process between YBa2Cu3O7−δ (YBCO) and iron particles. Fe diffusion into the YBCO matrix could be fundamental for multilayer systems with YBCO/Fe-alloy interfaces. We have found that the orthorhombic YBCO structure adopts to 3 wt% Fe, while for higher Fe content, a formation of BaFeO3−δ and iron oxides was observed. Complementary measurements confirmed the strong superconductivity suppression in YBCO-Fe materials containing more than 7 wt% Fe. The YBCO with diffused Fe material retain the unit cell orthorhombicity (max. 3 wt% Fe), and their superconducting properties follow the principle of critical scaling with different exponents (γ). The critical current density (Jc), pinning fields (HP) exhibit γ = 1, the first critical field (Hc1) shows γ = 1/2, and critical temperature (Tc) demonstrates γ = 7/4. 相似文献
993.
Manal A. Mahdy Sayed H. Kenawy Esmat M.A. Hamzawy Gehan T. El-Bassyouni I.K. El Zawawi 《Ceramics International》2021,47(9):12047-12055
The influence of adding 10, 20 and 30% molar ratio of silicon carbide (SiC) separately to a composite of wollastonite (W) with a fixed content of 10%Fe2O3 prepared by wet precipitation method was studied. The crystal structure of the annealed composite powders was inspected by X-ray diffraction (XRD); revealing multi-phase structure. The highest estimated crystallite size investigated by Scherrer equation of W, SiC, WFe:SiC10, WFe:SiC20 and WFe:SiC30 were 53.89, 54.6, 56.3, 48.5 and 54.6 nm respectively; demonstrating the formation of nanocomposites. Particles shape, size and crystallinity of the samples were studied using high resolution transmission electron microscope (HR-TEM). The band gap Eg values of the nanocomposites increased with SiC content having an intermediate value that lies between that of γ-Fe2O3 (maghemite) and SiC. Ferromagnetic and paramagnetic contributions were observed in the magnetic hysteresis loops for the composites. This study highlighted that the coercive field (Hci) of the composites improved with increasing the SiC content. The innovative wollastonite/Fe2O3/SiC with amended magnetic properties elicited attention due to their promising application in bone filler and industrial purposes. 相似文献
994.
《Intermetallics》2015
The present work is devoted to fabrication of Fe–B–Si–Zr multi-component bulk glassy alloys with good mechanical and soft magnetic properties. Glass formation in Fe–B system is first considered with an empirical cluster-plus-glue-atom model. A basic composition formula [B–B2Fe8]Fe is proposed as the framework for multi-component alloy design. Considering the structural stability of the model glass, Si and Zr are introduced to the [B–B2Fe8] cluster to replace the center B and shell Fe atoms, from which a series of Fe–B–Si–Zr alloys with composition formulas [Si–B2Fe8−xZrx]Fe (x = 0–0.6) are derived. Copper mold casting experiment shows that bulk glassy alloys are formed within the Zr content range of x = 0.2–0.6, and the largest glass-forming ability appears at [Si–B2Fe7.6Zr0.4]Fe with a critical size of 2.5 mm. The bulk glassy alloys exhibit high fracture strength as large as 3850 MPa. Magnetic property measurement indicates that these alloys exhibit good magnetic softness with high saturation magnetization (1.26–1.48 T) and low coercive force (1.6–6.7 A/m). The alloying effects of Si and Zr on bulk glass formation, thermal glass stability and magnetic softness are discussed with the empirical model. 相似文献
995.
《Intermetallics》2015
In this article, we report the formation of the high-entropy Gd20Tb20Dy20Al20M20 (M = Fe, Co and Ni) bulk metallic glasses with good magnetocaloric properties. Compared with most of the rare earth based metallic glasses, these alloys are found to have the comparably large maximum magnetic entropy changes (ΔSM), but much broader widths of the ΔSM peaks, and hence larger refrigerant capacity (RC). This can be attributed to the combination of the spin glass behaviors and the complicated compositions in these alloys. Our work show that the high entropy bulk metallic glasses is a promising candidate material as the magnetic refrigerant. 相似文献
996.
《Ceramics International》2015,41(7):8637-8642
Manganese ferrite nanoparticles were electro-crystallized in an electrochemical cell containing two iron electrodes, and an electrolyte solution of sodium sulfate, sodium butanoate, and manganese sulfate hydrate. The samples were characterized by X-ray diffraction, electron microscopy, magnetometry, and Mössbauer spectroscopy methods. The crystal structure of the samples was studied using X-ray diffraction. Based on obtained results we found that the manganese ferrite nanoparticles are formed in the electrochemical cell containing 0.001 M manganese sulfate hydrate. Also, the formation of a paramagnetic secondary phase in the sample without manganese is suppressed by adding manganese salt in the electrochemical cell. The nanoparticle size, shape, and morphology were characterized using electron microscopy. Magnetization curves show that all samples are magnetically soft and their specific magnetization ranges from 15 A m2 kg−1 to 75 A m2 kg−1, depending on the growth conditions. Room temperature Mössbauer spectra confirm the formation of nonstoichiometric spinel ferrite of magnetite or manganese ferrite, again depending on the growth conditions. Based on Mössbauer analysis, reduction in the population of octahedral sites provides direct evidence for the presence of the manganese ions substitution in the octahedral sites. 相似文献
997.
The influences of atmosphere during processes of melting and heat treatment, heat treatment temperature, Fe3O4 content and basicity on the magnetic properties of magnetite-based glass ceramics were investigated. For sample containing 20 % Fe3O4 melted in different atmospheres, the highest saturation magnetisation was realized in 20vol% air + 80 vol% Ar, due to the fact that ratio of Fe3+ to Fe2+ in melt obtained in this atmosphere was close to 2. However, it was found that the coercivity of glass ceramics was not affected by the melting atmosphere. A high sintering temperature led to the decrease of saturation magnetisation and the increase of coercivity. As increasing Fe3O4 content, the main crystal phase transformed from CaSiO3 to CaFe0.6Al1.3Si1.08O6 and finally to magnetite phase, accompanied by the increase of saturation magnetisation and coercivity. In addition, the increase of basicity caused the decrease of saturation magnetisation and the increase of coercivity. 相似文献
998.
Chuang Tian Qingrong Yao Zhaofei Tong Huaiying Zhou Guanghui Rao Jianqiu Deng Zhongmin Wang Jiang Wang 《中国稀土学报(英文版)》2021,39(7):835-843
In this paper,polycrystalline samples of Bi_(1-x)Sm_xFeO~3(x=0,0.05,0.1,0.15) were successfully synthesized by sol-gel method.The effects of Sm concentration on the crystal structure,morphology,chemical states,magnetic properties and microwave absorption performance were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),a vibrating sample magnetometer(VSM) and a Vector network analyzer(VNA),respectively.The results show that the rare earth Sm doping causes the crystal structure to change.When x≤0.1,Bi_(1-x)Sm_xFeO_3 is the distorted rhombohedral structure with space group R3 c.With the increase of Sm doping amount to x=0.15,the phase structure of Bi_(1-x)Sm_xFeO_3 changes from rhombohedral structure to cubic structure with the space group Pm3 m.The particle size decreases with the increase of the Sm doping amount.The analysis results show that Sm doping can effectively reduce the oxygen vacancies and significantly improve its magnetic properties.The results exhibit that moderately doped rare earth Sm element can effectively improve microwave absorption properties of Bi_(1-x)Sm_xFeO_3 powders.When Sm doping amount of x is 0.1,the Bi_(0.9)Sm_(0.1) FeO_3 compound has good microwave absorption performance,and the minimum reflection loss value of Bi_(0.9)Sm_(0.1)FeO_3 powder reaches about-32.9 dB at11.7 GHz,and its effective absorption bandwidth(RL -10 dB) is 2.6 GHz with the optimal matching thickness of 2.0 mm. 相似文献
999.
《Ceramics International》2020,46(5):6141-6145
The single phase Bi0.95Sm0.05Fe1-xNbxO3 (0 ≤ x ≤ 0.1) nanoparticles were synthesized by the sol-gel route, and the effect of Nb substitution on their magnetic, ferroelectric and photocatalytic properties were studied. X-ray diffractometry confirms a phase transformation from rhombohedral to orthorhombic with an increase in Nb substitution. The grain size decreases significantly, and the morphology of grains becomes homogeneous with the increase of Nb concentration. The maximum remnant magnetization (0.014 emu/g), coercivity (565 Oe) and polarization (0.592 μC/cm2) are observed in Bi0.95Sm0.05Fe0.9Nb0.1O3. It has been observed that the energy band gap has been slightly reduced from 2.14 to 2.03 eV with Nb substitution, indicating an improvement of photocatalytic activity. The methylene blue degradation is used to represent the photocatalytic ability of Bi0.95Sm0.05Fe1-xNbxO3 nanoparticles. The highest degradation efficiency (~74%) of methylene blue is obtained in Bi0.95Sm0.05Fe0.93Nb0.07O3, which is much higher than that of Bi0.95Sm0.05FeO3 (~51%) and can be attributed to the optimum particle size and the smallest energy band gap. 相似文献
1000.
Polyvinyl pyrrolidone (PVP) capped Zn1−xCrxO (0.000001≤x≤0.1) nanocomposites were successfully synthesized using a simple chemical co-precipitation technique. The synthesized nanostructures were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray fluorescence (EDXRF), Fourier-transform infrared spectroscopy (FTIR), UV–visible spectroscopy, photoluminescence (PL) and vibrating sample magnetometer (VSM) measurements. The structural characterization by XRD, TEM, FTIR and EDXRF confirmed the formation of wurtzite structure and incorporation of Cr in the ZnO lattice. The photocatalytic activities of as prepared nanocomposites were evaluated by degradation of methylene blue (MB) dye in aqueous solution under UV/sunlight light irradiation. The results demonstrated that Zn1−xCrxO (x=0.0001) nanocomposite effectively bleached out MB, showing as impressive photocatalytic enhancement over pure ZnO and ZnS nanoparticles. This enhanced photocatalytic activity at optimum concentration was attributed to increased absorption ability of light and high separation rate of photoinduced charge carriers on the nanocomposite photocatalyst surface. The VSM measurements showed significant ferromagnetism in Cr-doped ZnO nanostructures and the value of saturated magnetism was found to decrease with increase in Cr content. 相似文献